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The Geo Metro, like most other passenger cars, uses a 12-volt power system to supply the cars electrical needs. Unfortunately, the cars spark plugs require much higher voltage to create the spark that ignites the fuel-air mixture. The ignition coil provides this increased voltage by converting the 12 volts supplied by the electrical system into a charge of up to 30,000 volts. Quite often, when a car uses to run or runs badly, the fault lies with the ignition coil.

Instructions

1

Locate the ignition coil, connected to the cars firewall. It is a cylindrical object with a thick wire connected to it.

2

Remove the plastic cap that protects the coil.

3

Use a voltmeter to test the coils positive terminal. Set the voltmeter to 12-volt direct current (DC), and touch the positive probe to the positive terminal on the coil. The terminals are bolts on one end of the coil, and the positive terminal will be marked with "+." The voltmeter should read 12 volts. If not, proceed to Step 4.

4

Check to ensure that the ignition coil electrical connector is firmly in place. Check the under-hood fuse panel to ensure the coil fuse/relay has not gone bad. Blown fuses of this type appear burned. Recheck the coil with the voltmeter. If it still detects no power, the problem lies at a location other than the coil.

5

Disconnect the negative battery terminal to cut off power to the coil.

6

Disconnect the high-tension cable from the coil. This is the thick wire that attaches to the center of the coil using a connector similar to a spark plug boot. Grasp the boot, and pull it straight off the coil as you twist it.

7

Use a 1/4-inch drive socket or a small box end wrench to disconnect the negative and positive terminal wires from the coil.

8

Remove the coil from the firewall by removing the two bolts that attach the mounting bracket.

9

Set the voltmeter to test resistance (ohms), and touch the probes to the positive and negative terminals. The voltmeter should read between 1.35 and 1.65 ohms for standard-emission models, and between 1.08 and 1.32 ohms for cars with upgraded (California) emissions. If the reading falls outside this range, replace the coil.

10

Check the resistance between the positive terminal and the high-tension terminal just as you did in Step 9. This resistance should lie between 22.1 and 22.9 kilohms for all models. If the reading falls outside this range, replace the coil.

The name "Camry" is an anglicized interpretation of the cars original nomenclature "Kanmuri," which means "crown" in Japanese. Little could Toyota have known when it introduced the car in 1982 how appropriate that name would become, as the Camry would eventually be crowned the king of compact sedans in America.

Ignition Function

The basic purpose of any automobiles ignition system is to ignite the air/fuel in the cylinders. Three basic parts comprise the ignition system: the triggering mechanism that sends energy to the spark plugs, the ignition coil that amplifies the triggering energy to create a powerful spark and the spark plug that receives that energy to make the air/fuel mixture detonate. The shorter the distance between the ignition coil and plug, the less energy the system loses through resistance in the wire.

Coil Pack Ignition

Ideally, a spark plug should be connected directly to the ignition coil so that every bit of the coils energy goes into creating a spark. This wasnt practical on older, distributor-driven cars; the distributor itself was the weak link in the system, so the gains would have been minimal. It wasnt until the mid-1980s that computers and magnetic sensors were cheap enough, powerful enough and sophisticated enough to detect crankshaft position and trigger the coil without a distributor. Once these were mass-produced, manufacturers began using a computer to trigger multiple coils in a "coil pack." Each coil provided energy to two cylinders.

Direct Ignition

Direct ignition is an evolution of coil-pack ignition and uses a single coil mounted directly to the back of the spark plug instead of one coil for every two cylinders. Direct ignition is the most theoretically perfect ignition possible with todays technology, offering a very powerful, computer-controlled spark without relying on a single moving component. The Camry doesnt actually use a coil pack; it has direct ignition with one small coil-pack-style coil per cylinder.

Failure

One of the direct ignition systems strongest trump cards is that it uses solid-state technology. There are no moving parts to wear out; even the crankshaft position sensor is fully magnetic, so it cant wear out through normal use as a mechanical component would. Aside from computer failure, the only way that a direct ignition system can fail is if the coil itself internally shorts out or something happens to the wiring between the coils and the computer.

If you suspect ignition coil failure, simply unplug the wiring harness from the top of the plug and see if the engine changes pitch or idle quality. Of course, the Camrys on-board diagnostics system will already have detected a coil malfunction and triggered a check engine light, so this might action might not be necessary.